Highly elastic fleece

ABSTRACT

ELASTIC NON-WOVEN FIBROUS SHEET MATERIAL IS PRODUCED BY PREPARING A MAT FROM ELASTIC POLYURETHANE STAPLE FIBERS AND CELLULOSE, POLYAMIDE OR POLYACRYLONITRILE STAPLE FIBERS BY CARDING THE FIBERS IN LAYERS WITH THE ELASTIC POLYURETHANE FIBER BEING EMBEDDED BETWEEN TWO LAYERS OF CELLULOSE, POLYAMIDE OR POLYACRYLONITRILE FIBER AND CON-A SOLIDATING THE FORMED MULTILAYER TO AN ELASTIC NON-WOVEN FIBROUS SHEET MATERIAL. THE FIBROUS SHEET MATERIAL MAY THEN BE BONDED BY COATING THE SHEET MATERIAL WITH A BINDING AGENT.

United States Patent 3,565,745 HIGHLY ELASTIC FLEECE Karl-Arnold Weber, Cologne-Stammheim, Wolfgang Rellensmann, Dormagen, and Wolfram von Langenthal, Cologne-Bickendorf, Germany, assignors to Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Continuation of application Ser. No. 472,307, July 15, 1965. This application Sept. 2, 1969, Ser. No. 856,887 Claims priority, application Germany, July 28, 1964, F 43,593 Int. Cl. B32b 5/06, 5/28 U.S. Cl. 161154 4 Claims ABSTRACT OF THE DISCLOSURE Elastic non-Woven fibrous sheet material is produced by preparing a mat from elastic polyurethane staple fibers and cellulose, polyamide or polyacrylonitrile staple fibers by carding the fibers in layers with the elastic polyurethane fiber being embedded between two layers of cellulose, polyamide or polyacrylonitrile fiber and consolidating the formed multilayer to an elastic non-woven fibrous sheet material. The fibrous sheet material may then be bonded by coating the sheet material with a bind ing agent.

This application is a continuation of Ser. No. 472,307, filed July 15, 1965, now abandoned.

This invention relates to non-woven products, sheets and fleeces containing elastic polyurethane fibres. It is known to manufacture non-woven sheets and fleeces from any fibrous materials of natural or synthetic origin with the aid of binding agents in the form of aqueous dispersions, thermoplastic powders, shavings, granules or fibres or high molecular weight polymers in organic solvents. It is also known to reinforce fibrous webs by mechanical means, e.g. by needle punching.

The elastic behaviour of such fleeces depends both on the properties of the fibres and on those of the binding agent. Most of the known fibres have only a slight elasticity compared with that of rubber threads. Elastic fleeces can thus generally be produced only by reinforcing the fibrous web with natural or synthetic rubber in the form of latex. Both the distribution of binder and the shape of the bonding points influence the elasticity. However, the elasticity of such fleeces is still very low since the nonelastic fibres largely determine the mechanical properties of the fleece. Moreover, the deformability of the binding areas is limited owing to the slight capacity of these areas for expansion and has therefore only a slight influence on the elastic stretchability of the sheet structure.

The use of binders containing butadiene polymer has the disadvantage that the bonded fabrics are sensitive to the action of light, heat and oxygen and undergo yellow ing within a relatively short time. If, on the other hand, age-resistant binders based on polyacrylic acid esters and their derivatives are employed, the products obtained have an even much lower elasticity.

It has now been discovered that elastic non-woven fibre products such as sheets and fleeces are obtained by producing fleeces from at least to 100% of elastic polyurethane fibres and between 90 and 0% of other fibres. The other fibres used for the production of the web may be of natural or synthetic origin, e.g. fibres of cellulose, polyamide or polyacrylonitrile. As elastic polyurethane fibres there may be used fibres from spandextype, e.g. prepared from polyether or polyester-diiso- "ice cyanate addition products and a chain extending agent such as a diamine, a hydrazide, a glycol or water. The obtained fleece has a tensile strength of at least 10 kiloponds per mmf Such a fibre web can be bonded with any known binder by the usual processes comprising introduction of the binder in the form of an aqueous dispersion or aqueous or organic solution followed by drying and cross-linking of the binder by the action of heat or time or by incorporating thermoplastic fibres, powders, granulates or shavings, for example of polyethylene, polyvinyl chloride or polyamide, into the fibre web, followed by welding, or by plasticisiug the polyurethane fibres. The fibre fleeces may be consolidated by processes which are known per se, for example by a mechanical strengthening process, e.g. on the needle loom, is possible in the same way as in other fibre webs. The fleeces obtained are distinguished by very high elasticity which depends mainly on the percentage content of the elastic polyurethane fibres in the total fleece. If adhesive or mechanical strengthening of the polyurethane fibre fleece is carried out while the polyurethane fibres are in the expanded state or if the fibres are stretched during the strengthening process, e.g. by very dense stitching of a web which has been delivered and removed in the exact dimensions or by stretching the fibres during the drying of the web impregnated with binder, the result is that when the tension which produces the expansion is released, the consequent contraction of the elastomeric fibres gives rise to a very dense sheet structure of high specific weight similar to fibre fleeces which have been compacted as a result of fibre shrinkage due to the action of heat or solvents or swelling agents or plasticising agents after strengthening process.

The polyurethane fibre fleeces compacted as described above have, however, the advantage over the shrunk fibre fleeces that they have a high elastic expansion, which is equivalent to increased resistance to repetitive mechanical stress because added to the high strength due to the high density there is an increase in flexibility. Fatigue phenomena therefore occur much later in the material than is the case with relatively rigid shrunk fibre fleeces.

In the strengthening of such fibre Webs, it is rather immaterial Whether an elastic or a hard or brittle binder is used since the elastic behaviour of the fleece material is determined mainly by the composition of the fibre and less by the binder components. The maximum content of polyurethane fibres in fibre mixtures that are capable of being crimped depends on the other fibre components employed and on the preparation of preliminary treatment of the polyurethane fibres. Thus polyurethane fibres which have not been pretreated can only be added to the extent of 10% to polyamide staple fibres. Mixtures having higher contents of polyurethane fibres can no longer be satisfactorily formed into an even web.

In the case of polyacrylonitrile fibres, this maximum content is 50% and in the case of cellulose fibres it is If the polyurethane fibres are prepared with lubricants, such as sodium salt of a fatty acid amide and/or an ester of a fatty acid or talcum, then mixtures having higher contents of polyurethane fibres or even webs made of pure polyurethane fibres can be formed. Care must however be taken to ensure that these lubricants do not impair the strengthening process. If this is the case, the fibre web must be freed from the lubricant before the application of binder of the welding process. This would usually be done by passing the web through a rinsing bath.

In the case of loose, mechanically strengthened webs, the elastic behaviour of the polyurethane fibres is only of slight importance since when the fibres are subjected to tension, they are more likely to become displaced in the fibre web than to be stretched alone. If the fibres are very tightly intertwined however, the elasticity of the polyurethane fibres plays an important role in the mechanical behaviour of the fleece.

If the fibrous web is strengthened with a binder which has an adhesive effect, care should be taken to adjust the proportion of binder in the total fleece so as to obtain the optimum elasticity. This optimum generally lies at a binder content of about 30% but may also be considerably higher or lower, in the region of 85% to of the total weight, if the binder has an elastic expansibility which is appropriate for the polyurethane fibre or a very low elastic expansibility. Since binders, which are applied from the aqueous phase, are generally deposited in droplet form at the points offibre intersection, the mechanical properties of the synthetic resin being only of minor importance for the elastic behaviour of the finished compound material. If, however, the binder is applied from an organic solvent, the tendency to film formation is much more marked. Care should therefore be taken to ensure that in this case the binder has the same or at least nearly the same elasticity as the polyurethane fibre. The following adhesive binders may be used:

The polymerisation products of the esters of acrylic acid and its derivation; polymers of the vinyl type, natural rubber, polybutadiene and its copolymers; polyesters preelongated with an isocyanate; polyurethanes etc.

These high polymer compounds can be applied either as aqueous dispersions or as solutions in organic solvents. Some of them are suitable for spinning fibres out of them. This means they can be incorporated in the web as bonding fibres.

The elastic bonded webs of the invention may be used in a manifold of technical fields i.e. as acoustical tiles, filter cloths, floor mats, furniture and car upholstery and plastic reinforcing.

In a specific embodiment of the invention an elastic non-woven fibrous sheet material being obtained by a process which comprises preparing a mat from elastic polyurethane (spandex-type) staple fibres by carding the fibres in layers, the elastic polyurethane staple fibre being between two layers of cellulosic or polyacrylonitrile fibres and consolidating the formed multilayer mat to an elastic non-woven fibrous sheet material. The consolidating process may be carried out as described above.

The following examples illustrate special embodiments of the invention.

EXAMPLE 1 -A non-woven fibrous mat consisting of 80% polyurethane fibre of the spandex-type, 2.75 den. 40 mm., and 20% cuprammonium cellulose fibre, 3.75 den. 60 mm. and having a weight per square metre of 110 g. is impregnated with butyl polyacrylate from the aqueous phase, dried at 70 C. and then cured for one minute at 150 C. The fleece obtained shows an elastic behaviour in the hys teresis curve. A non-woven elastic sheet may be prepared from 80% polyurethane fibre, the polyurethane fibre mat being located between two layers of cuprammonium cellulose fibres.

EXAMPLE 2 The fibrous mat mentioned in Example 1 is padded with a 30% solution of a diisocyanate-mQdifid polyester with a diisocyanate in ethyl acetate and the solution is then pressed into the web between foulard rollers. The web is then dried at 70 0., again pressed between foulard rollers and left to react for 24 hours. The fleece obtained gives the impression of leather and has good elasticity.

EXAMPLE 3 The fibrous mat described in Example 1 is needle punched on a needle loom and then compressedbetween two steel rollers heated to 180 C. arranged at a distance apart of about 0.2 mm. The fleece bonded in this Way showed good elasticity and high strength.

EXAMPLE 4 A fibrous mat consisting of 50% polyurethane fibre 0f the spandex type 2.75 den. mm. and polyacrylonitrile fibre 3.0 den. mm. and having a weight per square meter of 150 g. the polyurethane fibre mat being between two layers of the polyacrylonitrile (fibres is spraybonded with butyl polyacrylate from the aqueous phase, dried at 10 C. and then cured for 1 minute at 150 C. The resulting web is rather lofty and shows a good elasticity especially in horizontal directions.

EXAMPLE 5 A fibrous web consisting of polyurethane fibre of the spandex type 2.75 den. 40 mm. and 10% nylon 6 3.3 den. 60 mm. and having a weight per square meter of 45 g. is impregnated with butyl polyacrylate from the aqueous phase, dried at 10 C. and then cured for one minute at C. The resulting non-woven fabric shows a good elastic behaviour in the hysteresis curve and has a good abrasion resistance.

We claim:

1. An elastic non-woven fibrous sheet material comprising a layer of spandex-type polyurethane staple fibers interposed between two layers of cellulosic or polyacrylonitrile staple fibers and mechanically consolidated therewith, said polyurethane staple fibers comprising from about 50% to about 80% of the total fibers in said sheet material.

2; Sheet material of claim 1 wherein said layers are carded layers of staple fibers.

3. Sheet material of claim 1 wherein said layers are consolidated by needling.

4. Sheet material of claim 1 further containing an adhesive binder.

References Cited UNITED STATES PATENTS 2,978,785 4/1961 Wenzell et al. 28-72.2 3,007,227 11/1961 Moler 16ll81X 3,069,305 12/1962 Farh'bach et al. l6 ll56X 3,377,231 4/1968 Newman 16180 ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner US. Cl. XJR. 

